A conventional laser device disclosed in Patent Literature 1 is configured to cause multiple laser beams having different wavelengths to overlap one another on a dispersive element, which is a diffraction grating, to generate a single combined laser beam by utilizing a dispersive effect, and reflect a portion of this combined laser beam using a partially reflective mirror back into the laser media thus to form a resonator, and extract, as an output, a component of the combined laser beam that passes through the partially reflective mirror.